Process for preparing a catalyst support for polymerization of alpha-olefins, and support thus obtained

ABSTRACT

A process is provided for preparing a catalyst support for polymerizing α-olefins comprising the steps of: (i) reacting, in the presence of a first electron donor, a chlorine-containing organic compound and a prior mixture of an alkylmagnesien and an aluminoxane and/or aluminosiloxane and/or alkylaluminum and, optionally, a second electron donor; and (ii) activating a product from step (i) in suspension in an inert liquid by means of an activation electron donor, together with the support thus obtained, a catalyst for polymerizing α-olefins, comprising this catalyst support and a group IV transition metal halide, and a process for polymerizing α-olefins, particularly propylene, comprising contacting the α-olefin with the catalyst.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for preparing acatalyst support for (stereospecific) polymerization of alpha-olefins,in particular propylene, and to the support thus obtained.

[0002] Alpha-olefin polymerization in general is carried out usingZiegler-Natta type catalysts. The Ziegler-Natta type catalyst system isgenerally constituted by two non-dissociable elements: a transitionmetal-based catalytic component deposited on a magnesium chloride-basedsupport and a co-catalyst generally based on an aluminum compound.Numerous patents describe these catalyst components and their supports.

[0003] European patent application EP-A-0,239,475 discloses a controlledmorphology catalyst spherical support for alpha-olefin polymerization.The catalyst support is obtained by reaction a chlorine-containingorganic compound in the presence of an electron donor and a priormixture of an alkylmagnesien and an aluminoxane and/or aluminosiloxaneand, optionally an electron donor. The support is then subjected to anactivation step using a chlorine-containing compound prior toimpregnation by a transition metal halide. This process leads toeffective catalysts for ethylene polymerization. They have howeverproved to be less effective in particular for polymerization ofpropylene.

[0004] Activation of catalyst supports by treatment with cyclicmonoethers for ethylene polymerization catalysts is known. Europeanpatent application 0,554,141 discloses, for example, a process foractivating a magnesium chloride-based support that enters into themanufacture of the ethylene catalytic polymerization component. Thisprocess comprises activating the support in suspension in an inertliquid using a cyclic mono-ether. That patent does nevertheless notdisclose nor suggest the possibility of such activation for controlledmorphology catalyst supports adapted to propylene polymerization.

[0005] U.S. Pat. No. 3,642,746 discloses a Ziegler-Natta catalyst systemuseful to reduce the ash content of the obtained polymer. The catalystis prepared by pretreatment of a divalent metal dihalide with enelectron donor and impregnation of the obtained support with atransition metal halide.

[0006] A process for polymerization of ethylene in the gas phase leadingto a linear polyethylene with a narrow weight distribution is known fromU.S. Pat. No. 5,055,535. This process uses a Ziegler-Natta catalyst inpresence of an alkylaluminium and a monoether. According to thisdocument, the monoether should not be in contact with the catalyst inabsence of the cocatalyst in the medium. The monoether constituestherefore an external Lewis Base and intervenes only during thepolymerization. Further the monoether does not act as a polymerizationactivator and does therefore not allow to enhace productivity.

[0007] It is known that stereospecific polymerization of α-olefinsbeyond ethylene such as propylene requires a stereospecific typecatalyst. Indeed, contrary to polymerization of ethylene, which is asymmetrical molecule, the polymerization of an asymmetric α-olefin, suchas propylene, can lead to isotactic, syndiotactic or atactic chaining.The use of a stereospecific catalyst can then ensure that polymers ofthe desired structure, such as predominantly syndiotactic or isotactic,for example, are obtained. This explains why catalysts employed forethylene polymerization are not necessarily suitable for polymerizingpolypropylene.

SUMMARY OF THE INVENTION

[0008] It has now been surprisingly found that activation adapted toethylene can be applied to a support adapted to propylene.

[0009] The invention makes it possible to obtain catalysts which areboth highly effective and highly stereospecific for the polymerizationof α-olefins with at least 3 carbon atoms, in particular propylene.

[0010] The invention consequently pros ides a process for preparing acatalyst support for polymerizing α-olefins comprising the steps of:

[0011] (i) reacting, in the presence of a first electron donor, achlorine-containing organic compound and a prior mixture of analkylmagnesien and an aluminoxane and/or aluminosiloxane and/oralkylaluminum and, optionally, a second electron donor; and

[0012] (ii) activating the product from step (i) in suspension in aninert liquid by means of an activation electron donor.

[0013] The invention also provides a catalyst support obtainable by theprocess according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The invention will now be described in more detail below.

[0015] According to the invention, the spherical catalyst support isprepared by reacting, in the presence of an electron donor, achlorine-containing organic compound with a prior mixture of analkylmagnesien and an organic compound of aluminium, aluminoxane and/oraluminosiloxane and/or alkyl-aluminum. The chlorine containing organiccompound is caused to react in the prior mixture of alkylmagnesien andorganic compound of aluminium, the reaction taking place in the presenceof a first electron donor. The prior mixture of alkyl magnesien andorganic compound of aluminium can also comprise a second electron donor,which, generally. (but not necessarily) is of the same type as the firstelectron donor.

[0016] The reaction is carried out in the presence of a donor, which canbe introduced:

[0017] through previous mixing of the chlorine-containing organiccompound with this (first) donor; or

[0018] through previous mixing of the alkylmagnesien and aluminiumorganic compound (aluminoxane and/or aluminosiloxane and/oralkylaluminum) in this (first) donor; or

[0019] both through previous mixing of the chlorine-containing organiccompound in this (first) donor and previous mixing of the alkylmagnesienand organic compound of aluminium (aluminoxane and/or aluminosiloxaneand/or alkylaluminum) in this (second) donor. In this case, the seconddonor can be identical to or different from the first donor; it ispreferably identical.

[0020] According to one embodiment, the chlorine-containing organiccompound is mixed with at least a portion of the first electron donorprior to the reaction of step (i), this portion being preferably atleast 50%.

[0021] According to one embodiment, the amount of first electron donormixed with the chlorine-containing organic compound prior to thereaction of step (i) represents, in moles, more than 50% of the total ofthe first and second electron donors present during the reaction of step(i).

[0022] In a further embodiment, the reaction of step (i) takes place inthe presence of a first electron donor, the prior mixture of analkylmagnesien and an aluminoxane and/or aluminosiloxane and/oralkylaluminum comprising a second electron donor, identical to the firstelectron donor.

[0023] At the end of step (i), the solid obtained is generallysubstantially spherical.

[0024] The alkylmagnesien is previously mixed with the aluminoxaneand/or aluminosiloxane and/alkylaluminium, preferably in solution in aninert solvent such as a hydrocarbon, for example hexane or heptane,preferably in the presence of an electron donor, which can be the firstor second donor depending on the case. Once the mixture has been made,the chlorine-containing organic compound, generally (but notnecessarily) diluted in a (first) electron donor and optionally in aninert solvent such as hydrocarbon like hexane or heptane is made toreact. At the end of the reaction, the support formed, in suspension inthe reaction medium, is filtered and optionally washed with inertliquid. The support, in suspension in an inert solvent such as ahydrocarbon like hexane or heptane, is then brought into contact with aso-called activation electron donor, preferably a cyclic ether. Thisactivation operation can be carried out before or after the precedingfiltration and washing operations. The support formed is filtered andoptionally washed with an inert liquid if the cyclic ether treatmenttook place after the first filtration and first washing operations. Onethus obtains a support the particle diameter of which is generallycomprised between 5 and 150 microns and more generally between 10 and100. The supports and, consequently the subsequent catalysts have a verynarrow granulometric distribution width, in general less than 5. Thegranulometric distribution width of the final polymers is also narrowgiven that the polymerization process generally does not generate fines,in other words does not damage the growing particle duringpolymerization. This granulometric distribution width is characterizedby span measurement where the span is equal to (D90-D10)/D50 whereinD90, D10 and D50 represent the diameter below which respectively 90%,10% and 50% by weight of the particles is respectively found. The finalpolymers generally have a span value less than 5 preferably less than 2

[0025] The alkylmagnesien implemented corresponds to the formula R1MgR2wherein R1 and R2 are alkyl radicals having 1 to 12 carbon atoms.

[0026] The aluminoxane which may enter into the composition of thesupport is selected from products having the formula:

[0027] wherein R′ is an alkyl radical having 1 to 16 carbon atoms, theR″s forming together an O-radical or each representing an R′ radical andn is an integer from 0 to 20.

[0028] The aluminosiloxane which may enter into the composition of thesupport is selected from products having the formula:

[0029] wherein R1, R2, R3, R4, R5 which may be identical or different,represent an alkyl radical having 1 to 12 carbon atoms. preferably 1 to6 carbon atoms or yet again a hydrogen atom, preferably under theproviso that there are not more than three hydrogen atoms per mole ofderivative, or finally a chlorine atom, preferably under the provisothat there are not more than three chlorine atoms per mole ofderivative.

[0030] The alkylaluminium which may enter into the support compositionis selected from products having the formula A1R1R2R3 wherein the groupsR1, R2 and R3 have the same definition as above.

[0031] The chlorine-containing organic compound, acting as achlorinating agent for the alkylmagnesien derivative and aluminumorganic compound is selected from alkyl chlorides wherein the alkylradical is primary, secondary or tertiary and optionally comprises aheteroatom, said radical comprising up to 12 carbon atoms, preferably upto 7 carbon atoms among the alkyl polyhalides or among 2 the acidchlorides. Preferred compounds are tertiobutyle chloride, n-butylchloride. dichloroethane, thionyl chloride, benzoyl chloride.

[0032] The reaction is carried out in the presence of a first electrondonor and optionally a second donor introduced by the prior mixing of analkylmagnesien and an aluminum organic compound.

[0033] These first and second electron donors that may be identical ordifferent can be selected from the aliphatic or cyclic monoethers andaliphatic or cyclic diethers, aromatic or aliphatic carboxylic acids andtheir alkyl esters, ketones, vinyl esters, acrylic derivatives, inparticular alkyl acrylate or methacrylate, and the silanes. The esterscan also be employed in the form of addition products with Lewis acidhalides different from the dihalides of magnesium. Particularly suitedas first and second electron donors are compounds such as methylparatoluate, ethyl benzoate, ethyl acetate or butyl acetate, ethylether,ethyl para-anisate, dibutylphtalate, dioctylphtalate,diisobutylphtalate, acetone, methylisobuthylketone, vinyl acetate,methyl methacrylate, phenyltriethoxysilane,cyclohexylméthyl-diméthoxysilane, dicyclopentydiméthyoxysilane,2,2-diisobutyl-1,3-dimethoxypropane, 2.2-diisobutyl-1,3-diéthoxypropane,2-isopropyl-2-isobutyl-1,3-dimethoxypropane,2-isopropyl-2-cyclohexyl-1,3-dimethoxypropane,2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane,2,2-dicyclopentyl-1,3-dimethoxypropane, 9,9-bis(methoxyméthyl)fluorene,diisoamylether, sec-butylether, tetrahydrofuranne and dioxane. It isalso possible to employ any mixture of the above compounds.

[0034] The first and second electron donors are preferably aliphatic orcyclic ethers, notably diisoamylic ether, sec-butylether ortetrahydrofuranne. Particularly preferred are the aliphatic ethers.

[0035] In order to excercise strict control of the morphology of thefinal support, it is preferred to associate the components with eachother in appropriate amounts. Thus, the Mg/Al molar ratio is comprisedbetween 5 and 200, preferably between 10 and 80. Chlorine-containingorganic compound concentration is such that the Cl/Mg molar ratio ispreferably above 2, advantageously it is comprised between 2 and 4. Theamount of second electron donor to be implemented with thealkylmagnesien derivative, and the aluminum organic compound is suchthat the molar ratio of the second electron donor to the magnesium iscomprised, preferably, between 0.01 and 5. The amount of first electrondonor to be implemented with the chlorine-containing agent is such thatthe molar ratio of this first electron donor to magnesium is comprised,preferably, between 0.01 and 5.

[0036] In the framework of this invention, the support such as describedabove is treated, in suspension in an inert solvent, by an activatingelectron donor. The molar ratio between activation electron donor andmagnesium initially introduced is generally comprised between 0.1 and 3.To avoid any deterioration of the magnesium chloride-based support, itis desirable for the activation electron donor to be highly diluted inthe inert liquid. The volume ratio between the inert liquid andactivation donor is generally comprised between 1 and 20, preferablybetween 1 and 10. This treatment can be done with stirring at atemperature comprised between 20° C. and (Teb+20° C.). Teb being theboiling point of the activation electron donor. Preferably, thistemperature is comprised between 20° C. and (Teb−10C.). In this range ofpreferred temperatures, the support and catalyst are more solid and lessfines (with span elevation) are produced during polymerization. Theactivation electron donor is preferably a cyclic ether selected from themonoethers the oxygen of which forms a cycle having at least 4 and atthe most 12 carbon atoms. It is not excluded for some of the carbonatoms of the cycle to be bound to substituant hydrocarbon radicals, thetotal number of carbon atoms of the cyclic ether not exceeding. in thiscase, 16. Among these ethers. the following can be cited:tetrahydrofuranne. tetrahydropyrane, 2-methyl-tetrahydrofuranne, 3-methyl-tetrahydropyrane, tetrahydrofuranne being preferred.

[0037] The supports according to the invention are particularly suitablefor producing Ziegler-Natta catalysts for olefin polymerization, basedon halides of group IV (transition metal such as titanium.

[0038] The support is for example impregnated with transition metalhalide, more particularly of formula Ti(OR)nX4-n where R is an alkylradical with 1-12 carbon atoms, X is a halogen and n is an integercomprised between 0 and 4, preferably TiCl14. Impregnation can be doneconventionally by adding a sufficient amount of transition metal halideto the support, optionally in an inert solvent to form a homogeneoussuspension. Such impregnation can be done in the presence of an electrondonor. The support can optionally undergo two or more successiveimpregnations with the compound of general formula Ti(OR)nX4-n, whereineach impregnation may or may not be carried out in the presence of an(impregnation) electron donor.

[0039] The invention also provides a process for preparing a catalyst.

[0040] The impregnation electron donors suitable for the preparation ofsupported catalysts are organic compounds comprising one or severaloxygen, nitrogen, sulfur or phosphorus atoms. By way of example we cancite organic acids, organic acid esters, alcohols, ethers, aldelhydes,ketons, amines, amine oxides, amides, thiols. The association of one orseveral of the above electron donors can be implemented. Morespecifically, the currently employed electron donors containing one orseveral oxygen atoms can be organic acid esters or ethers. Morespecifically, these can be mono- or dicarboxylic aromatic esters ordiethers. Examples of aromatic esters are the dialkylphtalates whereinthe alkyl group contains 1-20 carbon atoms, preferably 1 to 10 carbonatoms, such as di(n-butyl)phtalate, diisobutylphtalate, dioctylphtalate,diheptylphtalate, diethylphtalate. The following examples of dietherscan be cited: 2,2-diisobutyl-1,3-dimethoxypropane,2,2-diisobutyl-1,3-diéthoxypropane, 2-isopropyl-2-isobutyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclohexyl-1,3-dimethoxypropane,2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane,2,2-dicyclopentyl-1,3-dimethoxypropane, 9,9-bis(methoxyméthyl)fluorene.

[0041] The amount of impregnation electron donor can vary. Withadvantage, it is comprised between 2 and 20% and preferably between 4and 16% by weight of the catalytic component.

[0042] According to one embodiment, the amount of impregnation electrondonor is less than 9% by weight of the catalytic component. According tothis embodiment, the production of polyalphaolefin having a widenedmolecular weight distribution is favored.

[0043] According to another embodiment, the amount of impregnationelectron donor is greater than 9% by weight of the catalytic compound.In this embodiment, a supported catalyst is obtained having very highproductivity. Suitable inert solvent for the synthesis of Ziegler-Nattacatalyst are the aliphatic hydrocarbons such as hexane, heptane ordecane, alicyclic hydrocarbons such as cyclohexane or ethylcyclohexane,aromatic hydrocarbons such as toluene, xylene or chlorobenzene or anymixture of the above solvents.

[0044] The catalytic component thus prepared is associated with aco-catalytic system for providing, olefin polymerization. Thiscocatalytic system is constituted by a cocatalyst and, optionally, anelectron donor. The cocatalyst is generally chosen from group III metalalkyls. Among these products we can mention: the alkylaluminiums such astrimethylaluminium, triethylaluminium, triisobutylaluminium andcombinations thereof. The cocatalytic electron donor can be selectedfrom the aliphatic or aromatic silanes of general formula SiR4 wherein Rcan be an alkyl group containing 1 to 20 carbon atoms and/or an alkoxy.OR′ group, R′ being an alkyl group containing 1 to 20 carbon atoms. Thecocatalytic electron donor can also be chosen from the family ofsilacycloalkanes. The cocatalytic electron donor can also be chosen fromthe family of diethers of general formula R1R2C(CH20R3)2, R1, R2 and R3can be alkyl groups containing 1 to 20 carbon atoms. As cocatalyticelectron donor. one for example will prefer dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxy-silane,diisobutyldimethoxysilane.

[0045] The invention applies to polymerization of α-olefins and moreparticularly propylene, as well as copolymerization or terpolymerizationof α-olefins. In the case of copolymerization the other monomer can beethylene or another monomer. When the comonomer is not an α-olefin, itmakes up less than 50% by weight. The term α-olefin such as employed inthis specification covers olefins comprising 3 to 20 carbon atoms,preferably 3 to 8 carbon atoms. The preferred α-olefin is propylene. Inthe case of copolymers of propylene, for example with ethylene orbutene, the comonomer generally makes up less than 30% by weight. Inaddition to the stereospecific polymers which may be made using thecatalyst of the invention, the catalyst also makes it possible toprovide, with high productivity, non stereospecific polymers such asrandom copolymers of α-olefins having a high ratio of a comonomer suchas ethylene.

[0046] The α-olefin polymerization can be done using known processes, insolution, in suspension, bulk or in the gas phase.

[0047] Preferably, the mean diameter of the catalyst according to theinvention is comprised between 5 and 5 μm when used with a suspensionprocess and between 20 and 150 μm when used with a as phase process.

[0048] A chain transfer agent can be employed for controlling melt indexof the polymer to be produced. The chain transfer agent can be hydrogenintroduced in an amount of up to 90% and generally in the range 0.01 to60 mole-% of the total, olefin and hydrogen introduced in the reactor.This chain transfer agent makes it possible to obtain a given meltindex, knowing that the melt index increases when the amount of chaintransfer agent increases. The invention offers the advantage of causinglittle chain transfer agent to be consumed for a given melt index.

[0049] The invention also provides a process for α-olefin polymerizationcomprising the following steps:

[0050] (i) preparation of a support as described above;

[0051] (ii) activation Of the support as described above;

[0052] (iii) preparation of a catalyst on the activated support of step(ii), as described above;

[0053] (iv) contacting an α-olefin charge with the catalyst underpolymerization conditions.

[0054] The following examples are given by way of illustration of theinvention not by way of limitation.

EXAMPLES

[0055] All handling is carried out under nitrogen atmosphere. HI isdefined as the percentage of polymer insoluble in boiling heptane. Themelt index is defined as in ASTM-D 1238.

Example 1

[0056] Synthesis of Support

[0057] In a glass 1 liter reaction vessel provided with a double jacket,mechanical stirring, a condenser and a pipe allowing reagentintroduction, there were introduced 135 g of a solution comprising 20%by weight (0.24 mole) butylethylmagnesium (BEM) in heptane. 1.56 gdiisoamylether (0.01 mole), 9.16 g (0.006 mole) of atetrabutyldialuminoxane (TiBAO) 20% by freight solution in heptane. Thismixture was stirred for 1 hour at room temperature at 500 rpm. Thetemperature of the reaction mixture was then raised to 50° C.

[0058] Under the same conditions of stirring and at 50° C., using asyringe, a mixture consisting of 56.8 g (0.61 mole) tertiobutyl chlorideand 2.34 g (0.015 mole) diisoamylether were introduced at a rate of 35ml/h. Following introduction, stirring and temperature were kept at thepreceding values for two hours. The suspension thus obtained wasfiltered then washed three times successively using 100 ml hexane oneach occasion. The mixture was filtered after each washing.

[0059] The solid recovered was resuspended in 200 ml hexane, and thetemperature was brought up to 40° C. with stirring (250 rpm ). Underthese conditions, using a syringe. 33.6 g (0.46 mole) tetrahydrofuranne(THF) were introduced at a rate of 60 ml/h. Following this addition, themixture was kept at 40° C. with stirring for 15 minutes. The suspensionwas then filtered and the solid recovered, washed three times each timewith 200 ml hexane. Filtration was performed after each washing. A solidwas obtained.

[0060] Synthesis of Catalyst

[0061] This solid was suspended in 60 ml toluene at room temperaturewith stirring (250 rpm ). 178 ml of TiCl4 were added. The temperaturewas raised in 10 minutes to 85° C. When the temperature reached 50° C.3.42 g di-n-butylphtalate (DnBP) were added. The temperature was kept at85° C. for two hours. After filtration, 123 ml toluene and 7 ml TiCl4were added and stirring was performed for one hour at 85° C. Thisoperation was repeated 4 times. After the last filtration, 200 ml hexanewere added with stirring for 15 minutes at 70° C. Following filtration,the solid was dried for two hours at 70° C., 23.4 g of a catalyst C1were obtained, containing 1.9% titanium. 1 3.9% magnesium and 8.3% DnBP.D50 was 11.4 microns for a span of 0.6.

[0062] Polymerization

[0063] In a 3.5 liter metal reaction vessel provided with a doublejacket and mechanical stirring, previously put under inert atmosphere,one bar hydrogen and 2.4 liter propylene were introduced. Understirring, 24 mMoles triethylaluminium, 1.2 mMolesdicyclopentyldimethoxy-silane and 15 mg C1 catalyst were introduced atroom temperature. The temperature was raised to 70° C. in ten minutes,then kept at this value for one hour. The residual propylene was thendegassed and 605 grams of polypropylene were recovered, equivalent to40500 g polypropyle/gram of catalyst C1 having a melt index of 7.0gramme/10 minutes and an HI of 97.0%. D50=386; span=1.2;% fines=8.8(percentage of particles having a diameter below 100 micron).

Example 2

[0064] Synthesis of Support

[0065] In a glass 1 liter reaction vessel provided with a double jacket,mechanical stirring, a condenser and a pipe allowing the introduction ofreagents. 135 g of a solution constituted of 20% by weightbutylethylmagnesium (BEM) in heptane, 1.56 g diisoamylether, 9.16 g, ofa solution of tetraisobutyldialuminoxane (TiBAO) 20% by weight inheptane were introduced. This mixture was stirred for one hour at roomtemperature at 500 rpm. The temperature of the reaction mixture was thenraised to 50° C.

[0066] Under the same conditions of stirring and at 50° C., using asyringe, a mixture consisting of 56.8 g tertiobutyl chloride and 2.34 g.diisoamylether were introduced at a rate of 35 ml/h. After thisintroduction, stirring and temperature were kept at the previous valuesfor 2 hours. The temperature was then brought to 40° C. and stirringdecreased to 250 rpm. Using a syringes 33.6 g tetrahydrofuranne (THF)were introduced at a rate of 60 ml/h. Following this addition, themixture was kept at 40° C. with stirring for 15 minutes. The suspensionwas then filtered and the solid recovered was washed three times, usingon each occasion 200 ml hexane. A filtration was performed after eachwashing. A solid was obtained.

[0067] Synthesis of Catalyst

[0068] 20 g of this solid were suspended in 60 ml toluene at roomtemperature with stirring (250 rpm ). 160 ml of TiCl4 were added. Thetemperature was raised over 10 minutes to 100° C. When the temperaturereached 50° C., 3.06 g DnBP were added. The temperature was kept at 100°C. for 2 hours. After filtration. 123 ml toluene and 14 ml TiCl4 wereadded and stirred at 100° C. for 1 h. This operation was repeated 4times. After the last filtration, 200 ml hexane were added with stirringfor 15 ml minutes at 70° C. This operation was repeated twice. Afterfiltration, the solid was dried for 2 hours at 70° C. 11.3 g of acatalyst C2 were obtained containing 2.0% titanium. 19.2% magnesium and8.8%, DnBP. D50 was 10.4 microns for a span of 1.1.

[0069] Polymerization

[0070] In a 3.5 liter metal reaction vessel provided with a doublejacket and mechanical stirring previously put under inert atmosphere,one bar hydrogen and 2.4 liter propylene were introduced. With stirring,24 mMoles triethylaluminium. 1.2 mMoles dicyclopentyldimethoxy-silaneand 15 mg C2 catalyst were introduced at ambient temperature. Thetemperature was raised to 70° C. in ten minutes then kept at this valuefor one hour. The residual propylene was then degassed and 800 grams ofpolypropylene were recovered equivalent to 53300 g polypropylene/gram ofcatalyst C2 having a melt index of 2.9 gramme/10 minutes and an HI of98.2%. D50=360 μm; span=1.0: % 0fines=10.

Example 3

[0071] Synthesis of Support

[0072] In a (glass 2 liter reaction vessel provided with a doublejacket, mechanical stirring and a pipe allowing the reagents to beintroduced. 400 g butylethylmagnesium (BEM) at 20% in heptane, 4.60diisoamylether, 18.09 g of a solution of 20% by weighttetraisobutyldialuminoxane (TiBAO) in hexane were introduced.

[0073] This mixture was stirred for 1 hour at room temperature at 400rpm, the reaction mixture temperature being then raised to 50° C.

[0074] Under the same conditions of stirring and at 50° C. using asyringe, a mixture constituted of 168.3 g tertiobutyl chloride and 46.05g diisoamylether were introduced at a rate of 120 ml/h. After thisintroduction, the temperature was brought to 40° C. and stirring speedreduced to 250 rpm. Using a syringe, 99.6 g of THF were introduced at arate of 120 ml/h. Following this addition, the mixture was kept at 40°C. with stirring for 15 ml minutes. The suspension was then filtered andthe solid recovered, washed three times using 800 ml hexane on eachoccasion. A filtration was performed after each washing. A solid wasobtained.

[0075] Synthesis of Catalyst

[0076] 11.8 g of this solid were suspended in 31 ml toluene at roomtemperature with stirring (250 rpm), 94 ml of TiCl4 were added. Thetemperature was raised over 10 minutes to 100° C. When the temperaturereached 50° C. 1.81 g DnBP were added. The temperature was kept at 100°C. for two hours. After filtration, 7.7 ml of TiCl4 and 146 ml toluenewere added and stirring was performed for 1 hour at 250 rpm at 100° C.This operation was repeated three times. After the last filtration, 118ml hexane were added and stirring at 250 rpm was performed for 15 mlminutes at 70° C. This operation was repeated twice. After filtration,the solid was dried for 2 hours at 70° C. 7.3 g of catalyst C3 wereobtained, D50=31.2 μm, span=1.1.

[0077] Polymerization

[0078] In a 8 liter metal reaction vessel with a double jacket andmechanical stirring, previously put under inert atmosphere, 1 barhydrogen and 6 liter propylene were introduced. With stirring, 30 mMolestriethylaluminium, 1.5 ml Moles dicyclopentyldimethoxy-silane and 30 mgC3 catalyst were introduced at room temperature. The temperature wasraised to 70° C. in ten minutes then kept at this value for one hour.With a temperature brought down to 25° C., the residual propylene wasdegassed and 1410 grams of polypropylene equivalent to 47000 gpolypropyle per gram of catalyst C3 were recovered, having a melt indexof 7.8 g/10 minutes. Dp5=932 μm, span=1.0:% fines=2.3. HI=97.9.

Example 4

[0079] Synthesis of Support

[0080] In a glass 1 liter reaction vessel provided with a double jacket,mechanical stirring and a pipe allowing the reagents to be introduced.200 g of butylethylmagnesium (BEM) at 20% in heptane, 2.5 gdiisoamylether, 9.05 g of a solution of 20% by weighttetraisobutyldialuminoxane (TiBAO) in hexane were introduced.

[0081] This mixture was stirred for 1 hour at room temperature at 400rpm, the temperature of the reaction mixture then being raised to 50° C.

[0082] Under the same conditions of stirring and at 50° C., using, asyringe, a mixture constituted of 84.4 g tertiobutyl chloride and 23.3 gdiisoamylether were introduced at a rate of 60 ml/h. After thisintroduction, the temperature was brought down to 40° C. and stirringspeed reduced to 250 rpm. Using a syringe, 50.9 g of THF were introducedat a rate of 60 ml/h. After this addition, the mixture was kept at 40°C. under stirring for 15 ml minutes. The suspension was then filteredand a solid recovered, washed three times using 200 ml hexane on eachoccasion. Filtration was carried out after each washing. A solid wasobtained.

[0083] Synthesis of Catalyst

[0084] 12.8 g of this solid were suspended in 34 ml of toluene at roomtemperature with stirring (250 rpm ), 102 ml of TiCl4 are added. Thetemperature was raised to 100° C. in ten minutes. When the temperaturereached 50° C., 1.96 of DnBP were added. The temperature was kept at100° C. for two hours. After filtration, 8 ml of TiCl4 and 158 ml oftoluene were added with stirring for 1hour at 250 rpm at 100° C. Thisoperation was repeated three times. After the last filtration, 128 ml ofhexane were added with stirring at 250 rpm for 15 ml minutes at 70° C.This operation was repeated twice. After filtration, the solid was driedfor 2 hours at 70° C. 6.7 g of catalyst C4 were obtained D50=19.7 μm,span=1.4. This catalyst contained 1.9% titanium, 18.9% magnesium and9.8% DnBP.

[0085] Polymerization

[0086] In a 8 liter metal reaction vessel with a double jacket andmechanical stirring, previously put under inert atmosphere, 0.3 barhydrogen and 6 liter propylene were introduced. With stirring, 30 mMolestriethylaluminium, 1.5 mMoles dicyclopentyldimethoxy-silane and 30 mg C3catalyst were introduced at ambient temperature. The temperature wasraised to 70° C. in 10 ml minutes then kept at this value for 1 hour.With temperature brought back to 25° C., the residual propylene wasdegassed and 1311 grams of polypropylene equivalent to 44700 gramspolypropylene per gram of catalyst C4 were recovered. having a meltindex of 2 g/10 ml minutes. D50=804 μm; span=1.2;% fines=6.2. Mw/Mn=6.8(Mw/Mn: polymolecularity or polydispersity index, the ratio of molecularmass in weight to molecular mass in number).

Example 5

[0087] Synthesis of Support

[0088] The procedure was identical to that in example 4.

[0089] Synthesis of Catalyst

[0090] The procedure was identical to that in example 4 except that the1.9 g of DnBP was replaced by 0.65 g DnBP. 6.6 g of catalyst C5 are nowobtained. D50=20.4 μm, span=1.3. This catalyst contained 2.6% titanium,19% magnesium and 5.4% DnBP.

[0091] Polymerization

[0092] Polymerization was performed as in example 4 but 0.35 bar ofhydrogen were introduced instead of 0.3 bar, 1218 g of polymer wererecovered equivalent to 40600 g polypropylene per gram of catalyst C5having a melt index of 10 g/10 min, Dp50=684 μm; span=1.2; fines=3%,Mw/Nn=16.1

Example 6 Synthesis of Support

[0093] The procedure was identical to that in example 4.

[0094] Synthesis of Catalyst

[0095] 13.1 g of this solid were suspended in 3 5 ml of toluene at roomtemperature with stirring (250 rpm ). 105 ml of TiCl4 were added. Thetemperature was raised over 10 minutes to 100° C. When the temperaturereached 50° C., 32.8 g of DnBP were added. The temperature was kept at100° C. for 2 hours. After filtration, 8.5 ml of TiCl4 and 162 ml oftoluene were added with stirring at 250 rpm at 100° C. for 1 hour. Thisoperation was repeated three times. After the last filtration, 131 mlhexane was added followed by stirring at 250 rpm for 15 ml minutes at70° C. This operation was repeated twice. After filtration, the solidwas dried for 2 hours at 70° C. 6.9 g of catalyst C6 were obtained.D50=20.9 μm; span=1.4.

[0096] This catalyst contained 1.7% titanium, 18.5% magnesium and 12.8%DnBP.

[0097] Polymerization

[0098] Polymerization was performed as in example 4 except that 0.35bars of hydrogen were introduced instead of 0.3 bars. 1863 g ofpolypropylene were recovered equivalent to 62100 g propylene per gram ofCatalyst C6 having a melt index of 4.8 g/10 minutes. Dp50=805 μm;span=1.2; fines=4.9%.

Comparative Example

[0099] Synthesis of Support

[0100] In a 1 liter class reaction vessel provided with a double jacket,mechanical stirring and a condenser and pipe allowing reagents to beintroduced, 135 g of a solution constituted by 20% by weight (0.24 mole)butylethylmagnesium (BEM) in heptane, 1.56 g diisoamylether (0.01 mole),9.16 g (0.006 mole) of a solution of 20% by weighttetraisobutyldialuminoxane (TiBAO) in heptane were introduced. Thismixture was stirred for 1 hour at room temperature at 500 rpm. Thetemperature of the reaction mixture was then raised to 50° C.

[0101] Under the same stirring conditions and at 50° C., using, asyringe, a mixture constituted of 56.8 (g (0.61 mole) tertiobutylchloride and 2.34 g (0.015 mole) diisoamylether were introduced at arate of 35 ml/h. After this introduction, stirring and temperature werekept at the preceding values for 2 hours. The suspension thus obtainedwas filtered and washed three times successively using 100 hexane oneach occasion. The medium was filtered after each washing.

[0102] The solid thus obtained was suspended in 150 ml toluene. Thetemperature was brought up to 110° C. and maintained at this value fortwo hours. After filtration, the operation was repeated. After the lastfiltration, the solid was suspended in 100 ml heptane and maintained at100° C. for 30 ml minutes, then filtered. This operation was repeatedthree times. The solid was dried at 70° C. for 1 hour. A solid, wasobtained.

[0103] Synthesis of Catalyst

[0104] 5 g of this solid were suspended in 31.5 ml of toluene at ambienttemperature with stirring (250 rpm ), 94.6 ml of TiCl4 were added. Thetemperature was raised over 10 ml minutes to 90° C. When the temperaturereached 50° C., 1.75 ml of DnBP were added. The temperature Wasmaintained at 90° C. for 2 hours. After filtration, 30 ml of TiCl4 and270 ml of toluene there added with stirring at 100° C. for 1 hour. Thisoperation was repeated 4 times. After the last filtration, 100 ml hexanewere added with stirring for 1 5 ml minutes at 70° C. This operation wasrepeated twice. After filtration, the solid was dried for 30 ml minutesat 70° C. A catalyst C7 was obtained containing 0.28 titanium, 23.7%magnesium. D50 was 33.2 μm for a span of 1.3.

POLYMERIZATION

[0105] In a 3.5 liter metal reaction vessel with a double jacket andmechanical stirring, previously put under inert atmosphere, 0.35 barhydrogen and 2.4 liter propylene were introduced. With stirring, 24mMole triethylaluminium, 2.4 mMole dicyclopentyldimethoxysilane and 3 mgC7 Catalyst were introduced at ambient temperature. The temperature wasraised to 70° C. in ten minutes then kept to this value for 1 hour. Theresidual propylene was then degassed and 69 grams of polypropyleneequivalent to 2300 g polypropylene/gram of Catalyst C7 were recovered.

[0106] The invention is not limited to the embodiments described but maybe subject to numerous variations readily accessible to those skilled inthe art.

[0107] Although the invention has been described in conjunction withspecific embodiments, it is evident that many alternatives andvariations will be apparent to those skilled in the art in light of theforegoing description. Accordingly, the invention is intended to embraceall of the alternatives and variations that fall within the spirit andscope of the appended claims. The above references are herebyincorporated by reference.

What is claimed is: 1.- A process for preparing a catalyst support forpolymerizing α-olefins comprising the steps of: (i) reacting, in thepresence of a first electron donor, a chlorine-containing organiccompound and a prior mixture of an alkylmagnesium and an aluminoxaneand/or aluminosiloxane and/or alkylaluminum and, optionally a secondelectron donor; and (ii) activating the product from step (i) insuspension in an inert liquid by means of an activation electron donor.2.- The process according to claim 1, wherein the chlorine-containingorganic compound is mixed with at least a portion of the first electrondonor prior to the reaction of step (i). 3.- The process according toclaim 1, wherein the amount of first electron donor mixed with thechlorine-containing organic compound prior to the reaction of step (i)represents, in moles, more than 50% of the total of the first and secondelectron donors present during the reaction of step (i). 4.- The processaccording to claim 1, wherein the reaction of step (i) takes place inthe presence of a first electron donor, the prior mixture of analkylmagnesium and an aluminoxane and/or aluminosiloxane and/oralkylaluminum comprising a second electron donor, identical to the firstelectron donor. 5.- The process according to claim 1, wherein the firstand second electron donors are aliphatic or cyclic ethers, preferablyaliphatic ethers. 6.- The process according to claim 5, wherein thefirst and second electron donors are selected from diisoamylether andsec-butylether. 7.- The process according to claim 1, wherein thealuminosiloxane and/or alkylaluminum and the alkylmagnesium are employedin a molar ratio Mg/Al comprised between 5 and 200, preferable between10 and
 80. 8.- The process according to claim 1, wherein theconcentration of chlorine-containing organic compound is such that themolar ratio Cl/Mg is greater than 2, advantageously comprised between 2and
 4. 9.- The process according to claim 1, wherein the amount ofsecond electron donor employed with the derivative of alkylmagnesium andthe aluminoxane and/or the aluminosiloxane and/or alkylaluminum is suchthat the molar ratio of this electron donor to magnesium is comprisedbetween 0.01 and
 5. 10.- The process according to claim 1, wherein theamount of the first electron donor employed with the chlorine-containingorganic compound is such that the molar ratio thereof to magnesium iscomprised between 0.01 and
 5. 11.- The process according to claim 1,wherein the chlorine-containing compound is a primary, secondary ortertiary alkyl chloride. 12.- The process according to claim 1, whereinthe activation electron donor is a cyclic monoether. 13.- The processaccording to claim 12, wherein the cyclic monoether is tetrahydrofurane,tetrahydropyrane, 2-methyl-tetrahydrofurane, 3-methyl-tetrahydrofurane.14.- The process according to claim 13, wherein the cyclic monoether istetrahydrofurane. 15.- The process according to claim 1, wherein theactivation electron donor molar ratio to magnesium initially introducedis in general comprised between 0.1 and
 3. 16.- The process according toclaim 1, wherein the volume ratio of inert liquid to activation electrondonor is comprised between 1 and
 20. 17.- The process according to claim1, wherein the activation step is carried out at a temperature comprisedbetween 20° C. and (Teb+20° C.), Teb being the boiling point temperatureof the activation electron donor. 18.- The process according to claim17, wherein the activation step is carried out at a temperaturecomprised between 20° C. and (Teb−10° C.). 19.- A process for preparinga catalyst support for polymerizing αolefins comprising the steps of:(i) reacting, in the presence of diisoamylether, tert.butylchloride anda prior mixture of butylethylmagnesium (BEM), tetraisobutyldialuminoxane(TiBAO) and diisoamylether, the molar ratio of Mg/Al being comprisedbetween 10 and 80, the molar ratio of Cl/Mg being comprised between 2and 4? The molar ratio of diisoamylether introduced with BEM and TiBAObeing comprised between 0.01 and 5 and the molar ratio of diisoamyletherintroduced with tert.butylchloride being comprised between 0.01 and 5;and (ii) activating the product from step (i) in suspension in an inertliquid by means of tetrahydrofurane, the molar ratio of tetrahydrofuraneto the initially introduced magnesium being comprised between 0.1 and 3and the volume ratio of inert liquid and tetrahydrofurane beingcomprised between 1 and
 20. 20.- A catalyst support for polymerizingα-olefins, obtainable by the process according to claim
 1. 21.- Acatalyst support for polymerizing α-olefins, obtainable by the processaccording to claim
 19. 22.- A catalyst for polymerizing α-olefinscomprising the catalyst support according to claim 1, and a group IVtransition metal halide. 23.- A catalyst for polymerizing α-olefinscomprising the catalyst support according to claim 19, and a group IVtransition metal halide. 24.- The catalyst according to claim 23,wherein the transition metal halide is TiCl₄. 25.- The catalystaccording to claim 22, further comprising an impregnation electrondonor. 26.- The catalyst according to claim 25, wherein the amount ofimpregnation electron donor is comprised between 2 and 20% and,preferably, between 4 and 16% by weight of the catalytic component. 27.-The catalyst according to claim 26, wherein the amount of impregnationelectron donor is less than 9% by weight of the catalytic component.28.- The catalyst according to claim 26, wherein the amount ofimpregnation electron donor is greater than 9% by weight of thecatalytic component. 29.- The catalyst according to claim 25, whereinthe impregnation electron donor is a dialkylphtalate. 30.- The catalystaccording to claim 22, having a mean diameter comprised between 5 and150 μm. 31.- A process for preparing a catalyst according to claim 22,comprising impregnating a support with a composition of a transitionmetal halide, optionally in the presence of an impregnation electrondonor. 32.- A process for preparing a catalyst according to claim 23,comprising impregnating a support with a composition of a transitionmetal halide, optionally in the presence of an impregnation electrondonor. 33.- A process for polymerizing α-olefins comprising contactingthe α-olefin with a catalyst according to claim
 22. 34.- The processaccording to claim 33, wherein the poly-α-olefin has a span of less than5, preferably less than
 2. 35.- The process according to claim 33,wherein the α-olefin is propylene. 36.- The process according to claim33, wherein a homopoly-α-olefin is produced.